Project Summary Poorly managed, Serious Mental Illness (SMI) puts individuals at increased risk for symptomatic relapses, functional impairment, medical complications, incarceration, victimization, self-injury, and suicide. Development and testing of innovative treatments which can improve illness management in this population is a critical public health priority. Several studies have shown that the majority of people with SMI use mobile phones, and that many are interested in engaging in Mobile Health (mHealth) interventions which leverage texting as a method to support their recovery. Our investigative team developed a patient-centered illness management intervention which is delivered by a new breed of clinician: the texting Mobile Interventionist (MI). The MI model leverages resources and infrastructure that are largely available in community mental health settings. A pilot study of the MI intervention yielded very promising results in terms of feasibility, acceptability, and patient engagement. Building on our preliminary research, the aims of the current proposal are to: 1) Evaluate the effectiveness of the MI intervention in people with SMI. We will conduct a randomized controlled trial (RCT) of the MI intervention compared to community-based treatment as usual in 230 individuals with SMI; 2) Examine the treatment target as a mediator of treatment effects. We will evaluate whether and to what extent our proposed treatment target (illness management), serves a mediating role in the impact of the MI intervention on primary (i.e., symptoms), secondary (i.e., recovery, hospitalizations), and tertiary (i.e., patient satisfaction with treatment) outcomes; and 3) Examine the strengths and barriers of the MI intervention, from patient, practitioner, and organizational perspectives. We will conduct in-depth qualitative interviews with a subset of 30 recipients of the MI intervention. Participants will be purposively sampled to include high, medium, and low engagement with the intervention. We will also conduct two focus groups with practitioners and organizational leaders to glean additional information about patient engagement, satisfaction, outcomes, and intervention viability from community practitioner and leadership perspectives. The ultimate objective of the proposed project is to evaluate a validated mHealth intervention that can be realistically integrated into community mental health settings to increase the availability, reach, and broad impact of illness management approaches for people with SMI. A cadre of Mobile Interventionists that are trained to engage patients in their own environments using widely-available mobile phones may be a powerful new approach to strengthen services, improve patient outcomes, and reduce costs.